Air to air heat exchange, as a general concept, has been known for many years. See for example, U.S. Pat. No. 1,059,600 to Fisher, and U.S. Pat. No. 1,349,482 to Wood and U.S. Pat. No. 3,082,821 to Brown. In recent years, due to the rapid increase in the cost of energy, the use of heat exchangers has gained renewed interest. In general, an air to air heat exchanger provides for the exhausting of undesirable or polluted air from the interior of a building by replacing the foul air with fresh air from the exterior of the buildings, and does so in a manner that conserves the desirable heat energy contained in the exhaust air. This is typically accomplished with the use of exhaust and fresh air ducts lying adjacent each other and having a common heat exchange surface therebetween. Thus, as the warm exhaust air flows through the exhaust air duct, the warm air transfers its heat through the heat exchange wall to the cooler intake air as it flows through the intake duct and contacts the common heat exchange wall. In this manner, a significant portion of the heat content of the exhaust air can be conserved. Therefore an important aspect of a heat exchanger is the thermal efficiency thereof, i.e. the extent to which it can recover the heat from the exhaust air, and thus, minimize energy loss.
An example of a more recent heat exchanger is seen in U.S. Pat. No. 4,184,538 to Rauenhorst. The Ruenhorst device shows the use of turbulator bars within the heat exhaust duct for imparting turbulence to the exhaust air. This mixing of the exhaust air results in greater heat transfer by causing a greater percentage of the exhaust air to contact, and thus, release heat to the heat transfer surface.
However, the overall design and structure of prior art air to air heat exchangers limits their range of application. In particular, heat exchangers are needed in industry that offer improved resistance to corrosive environments, and that are not significantly impaired by highly humid indoor environments. In addition, it would also be desirable in commercial and residential applications to have a heat exchanger that occupies a minimum of space, and offers improved heat transfer efficiency.